Automatic control apparatus



Jan ZZ, 1935. w. s. ANDERSON. JR

AUTOMATIC CONTROL APPARATUS Filed April 1, 1950 INVENTOR WITNEIS s M ILLIAM SANDER-501$?! @251. a J; M 52.

Patented Jan. 72, 1935 UNITED STATES PATENT OFFICE signor to La Mont Corporation,

New York,

N. Y., a corporation of New York Application April 1,1930, Serial No. 440,835

18 Claims. (01. 122-406) This invention relates to automatic control apparatus, and more particularly to a construction which will serve to automatically maintain the delivery of fluid at a desired rate to a fluid system, and especially to the tubes of a steam generator.

Certain types of steam generators utilize a pump to create a forced circulation of water through steam generating tubes exposed to the heat of a furnace. In such an apparatus an adequate supply of water to the tubes is absolutely essential in order to prevent the tubes from reaching a dangerously high temperature. This has been recognized, and it has heretofore been 1:, proposed to utilize an auxiliary pump which will be automatically placed in operation in the event the main pump fails to maintain a predetermined pressure differential in the water flow circuit.

With such prior arrangements, however, it has been found that after the auxiliary pump has restored the desired pressure differential, the control device will immediately slow down the auxiliary pump and perhaps stop it entirely, whereupon the differential will fall once more and the control device will start the pump again, thereby causing a continuous hunting action. This results in defeating to a large extent the purpose of the auxiliary pump, since the delivery of water is intermittent and therefore may be inadequate to prevent the burning of the steam generating tubes. Similar problems arise in other types of apparatus utilizing main and auxiliary pumps.

With steam generators as heretofore con-' structed, the control apparatus has been subjected to a pressure differential which is independent ofv the rate of steam generation. Hence there has been no provision for increasing the rate of water delivery to the tubes as the steam generation increases, and it has been found that at high rates of steam generation the water supply to the tubes is sometimes insuflicientand the tubes have burned out.'

It is accordingly one object of my invention to provide a control apparatus which will serve to start an auxiliary pump automatically upon failure of a main pump to function properly, and which will thereafter maintain the auxiliary pump in continuous operation until shut down 50 manually.

It is a further object of my invention to provide a control apparatus which will start an auxiliary'pump automatically in the event a main pump should fail to maintain a desired condition of now, and which is so constructed that the auxiliary pump will continue in operation in spite of its having restored the said flow condition.

It is a further object of my invention to provide manually operable means for shutting down 5 the auxiliary pump which is so arranged that the auxiliary pump will not remain shut down unless the main pump is operating.

It is a further object of my invention to provide a control apparatus for a steam generator which is actuated in accordance with a pressure differential in the water circuit and which is so arranged that it will increase the rate of flow as therate of steam generation increases.

It is a further object of my invention to pro- 15 vide a control apparatus for the auxiliary pump in a steam generator which will automatically start the auxiliary pump whenever the rate of steam generation exceeds a predetermined value, even though the main pump is still operating properly. A further object is to provide a control apparatus for a pumping system which will be simple and inexpensive to manufacture and install, and which will be positive and reliable in operation.

With these and other objects in view,- as will be apparent to those skilled in the art, my invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

In accordance with one feature of my invention I provide a control apparatus for a main pump and an auxiliary pump arranged to discharge into a common system. The control apparatus-preferably comprises a movable device to control the power supply to the auxiliary pump, one suitable arrangement-,having-a fluid operated motor to drive the pump and a valve to control the fluid supply to the motor. This valve or other movable device is so constructed that it may be moved in a direction to start the auxiliary pump by means of a mechanism which is actuated automatically in accordance with flow conditions in the discharge of the main pump. This mechanism is, however, ineffective to move the device in the opposite direction, and the auxiliary pump will therefore continue its operation in spite of restoration of the flow conditions, failure of which causesitto start. Manually operable means is provided for restoring the various parts of the apparatus to their original positions after the main pump has been replaced in operation. e

As a further feature of my invention I provide a steam generating apparatus inwhich suitable 65 means, such as a pump, is arranged to positively force water into the generating element. I provide a control device for the pump which is actuated in accordance with a pressure differential in the water circuit which is dependent in value upon the rate of evaporation in-the generating element. I prefer to obtain this pressure differential by connections to the circuit close to and on opposite sides of a restriction, such as an orifice, at the entrance end of the generating element.

Referring to the drawing illustrating one embodiment of my invention, and in which like reference numerals indicate like parts,

Fig. 1 is a vertical sectional elevation of a steam generator;

Fig. 2 is an enlarged detail in section showing a pressure responsive switch mechanism;

Fig. 3'is an enlarged detail in section of a solenoid operated valve; and

Fig. 4 is an enlarged detail, in section showing a portion of the inlet header and one ofthe steam generating tubes.

The embodiment of the invention illustrated in the drawing comprises a furnace chamber 10 which is maintained at a high temperature by any suitable means. For this purpose I have shown an oil burner 11 arranged to deliver oil for combustion in the furnace in a well known manner.

A boiler 12 of any desired type is mounted above the furnace to absorb heat therefrom by radi-,

ation and convection. For simplicity of illustration, this boiler 12 has been shown as a horizontal cylindrical drum forming a receptacle for water and steam under pressure. It will be clear, however, from the following description that various other constructions may be utilized within the scope of the present invention. Water may be supplied to the drum 12 fromany suitable source through a feed pipe 14, and steam may be withdrawn from the drum through a pipe 15 leading to a main steam header 16.

Adjacent to one wall of the furnace chamber 10 I have shown a water wall comprising spaced parallel horizontal tubes 18 arranged to generate steam by the absorption of radiant heat from the furnace and to protect the refractory material of the wall behind them. The-tubes 18 are connected at one end to a vertical pipe or inlet header 19, and at their opposite ends to a vertical outlet he'ader 20. A suitable forcing means such as a centrifugal pump 22 driven by an electric motor 23, is provided to circulate water through the tubes. A pipe 24 is connected to the drum 12 below the water line and leads to the inlet of the pump 22. The discharge of the pump is connected to the inlet header 19 of the water wall by means of a pipe 26 provided with a check valve 27 of suitable construction to prevent reverse flow.- The outlet header 20- is connected by means of a pipe 28 with the steam space of the drum 12. I

With this construction the pump 22 draws water from the drum 12 through pipe 24 and delivers it under pressure through pipe 26 to inlet header 19 and tubes 18. The steam which is formed in the tubes, together with any unevaporated water, passes back to the drum 12 through header 20 and pipe 28. The entrance end of each tube 18 is preferably restricted by means of an'orifice plate 30 (Fig. 4) for the purpose of properly distributing the water among the tubes. I

The steam generating'tubes 18 are exposed to intense radiant heat, and it is absolutely essential to maintain an adequate supply of water to these tubes at all times to prevent them from burning out. Since there is a possibility that the pump 22 may become inoperative as a result of failure of the electrical "power supply to the motor 23, or for some other reason fail to supply a suflicient amount of water to the tubes, I provide a normally idle auxiliary pump 32 which is preferably connected in parallel with the main pump 22. The suction of the auxiliary pump 32 is connected to pipe 24, and the discharge of the pump is-connected to inlet header 19 by means of a pipe 33 provided with a check valve 34. The pump 32 may be driven by any suitable source of power, such as a fluid operated motor or steam turbine 36 supplied with steam from the header 16 by means of a pipe 3'7.

The present invention is primarily concerned with a control apparatus which will serve to start the pump 32 automatically upon failure of pump 22 to supply sufflcient water to the tubes 18, and which will maintain the auxiliary pump in operation in spite of the fact that its starting has resulted in restoring the desired flow conditions. For this purpose I prefer to utilize a control apparatus comprising a pressure responsive device, such as a flexible diaphragm 40 (Fig. 2) mounted in a suitable casing 41 and arranged to form pressure chambers 43 and 44 on opposite sides thereof. The pressure in the inlet header 19 is transmitted to chamber 43 through a pipe 45,

and the pressure in one of the tubes 18 close to creases, the steam velocity and resulting pressure drop due to friction in the tube will increase, and this will reduce both the rate of flow through the orifice and the pressure drop across the orifice. A compression spring 48 located in chamber 44 bears against the pressure plate 49 of the diaphragm and serves to oppose this pressure differential. A rod 51 is connected to the plate 49 and extends outside of chamber 44 through a stufling box 52, and this rod will move axially in response to variations in the rate of flow, since the pressure drop across the orifice plate 30 is a measure of this rate.

I utilize the axial movement of rod 51 to actuate a control device and start auxiliary pump 32 in the event the rate of flow falls below a predetermined value. One such control device which I have found suitable in many cases comprises a valve 54 located in the steam pipe 37 leading to the turbine 36. This valve includes a movable device or valve member 55 (Fig. 3) arranged to control the steam supply to the turbine and provided with a downwardly extending stem 56 on which is mounted an iron armature 58. An annular solenoid 59 is supported from the body of valve 54 by means of bracket members 60. This solenoid is coaxial with armature 58 and when energized serves to pull the armature upwardly and hold valve member 55 firmly against its seat. The valve is biased toward open position by gravity and the steam pressure. When the solenoid is de-energized the valve member 55, will therefore move downwardly andpermit steam to flow in the direction of the arrow in Fig. 3 to the turbine 36.

I provide a suitable electric switch to control the electric supply to solenoid 59, and to de-energize the solenoid in the event rod 51 should move a sufficient distance to the left in Fig. 2 in response to a drop in the rate of flow. The, preferred embodiment illustrated for accomplishing this purpose comprises a member 62 shaped as a rectangular block and supported by a stationary pivot spaced laterally from the center of gravity of the block, so that the block tends to swing downwardly about-the pivot under the influence of gravity. The pivot may be formed by a pin 63 extending through an arm 64 attached to the right hand end of the block as shown in Fig. 2. The left hand end of the block is normally supported by means of the rod 51. For this purpose I have shown a member 66 which projects laterally from the block 62 and rests on the rod 51. The member 66is preferably shaped as a latch pivoted to the block by means of a pin 67 and provided with a weighted end portion 68 which normally rests against the upper surface of the block and thus prevents the latch from turning about itspivot in a clockwise direction beyond the position shown in the drawing. It will now be seen that if rod 51 should move to the left to a predetermined position, it will release the block 62 and permit it to swing downwardly about its pivot 63.

I utilize this movement of the block to break the electric circuit through the solenoid 59, and I prefer to accomplish this result by mounting an electric switch 70 directly on the block itself. The switch '70 as illustrated is of the well known mercury type comprising a sealed glass bulb containing a small quantity of mercury. Two electrical contacts are sealed into the glass and are connected by the mercury when the switch is in the position shown. As the block swings downwardly the mercury will flow to the left end of the bulb, thus interrupting the circuit. The switch '70 is therefore biased by gravity to open position, and is normally held closed against its bias by the rod 51. Wires 71 serve to connect the switch in a circuit with solenoid 59 and a suitable electric power source '72.

I have found that under certain conditions the rod 51 tends to vibrate slightly in an axial direction, and that if the parts are not properly constructed there is a danger of the rod catching. on the end ofthe latch 8'7 as it starts to drop and thus causing damage to various parts of the mechanism. I have obviated this possibility in the construction illustrated by locating the pin 67 above the rod 51, so that if the rod should press against the latch it will merely swing it about the pin against the resistance of the weighted head 68. I also prefer to locate the pin 63 a substantial distance above the rod, since this causes the latch to swing away from the rod after it has been released. A handle 74 attached to the block 62 and extending downwardly through the casing provides a convenient manually operable means for resetting the latch after the main pump has been restored to operation, thus closing switch 70, energizing solenoid 59, closing valve 55, and shutting down the turbine 36.

It is desirable to provide means for adjusting the mechanism so that the latch may be automatically released at any desired minimum pressure differential. by adjusting the pivot pin 63 in a horizontal direction, thereby varying the amount by which the latch overlaps the rod 51. For this purpose I mount the pin 63 in the downwardly extending arm of a bell crank lever '76 pivoted to the casing at 7'! and provided with a horizontal arm. which This may be conveniently accomplished rests against an adjusting screw "18 in the casing. By turning this screw the setting of the mechanism may be easily varied. Pin 63 is preferably located out of line vertically with pin 77, so that the weight of the block 62 is effective to hold the lever 76 against the screw 78.

It is desirable to provide means for notifying the plant operator automatically of the starting of the auxiliary pump, so that he may investigate and remedy the difliculty which caused it to start. The preferred construction for this purpose comprises a second switch 80 mounted on the block 62 and connected by wires 81 into a circuit with a battery 82 and an electric bell 83. This switch is similar to switch 70 but is reversed in position so that it is open when in the position shown in Fig. 2, and closed after the block has swung downwardly. Switch 80 is therefore biased to closed position by gravity, but is normally held open against its bias by rod 51.

The operation of the invention will now be apparent from the above disclosure. Under normal conditions the main pump 22 is running properly and supplying water to the tubes 18 at a sulficient rate of flow. The diaphragm 40 is subjected to a pressure differential in excess of the desired minimum, and rod 51 being thereby forced to theright serves to support block 62 inthe position illustrated. Switch '70 is therefore closed, solenoid 59 is energized, valve 55 is held closed, and auxiliary pump 32 is idle. If now pump 22 should'cease to function properly for any reason, such as failure of the electric supply to the motor 23, or if the steam generation should reach an ex- 'tremely high rate and cause an excessive pressure drop along the tubes, the rate of flow of the water and the resulting pressure diflerential on diaphragm 40 will decrease, causing rod 51 to move to the left. Block 62 will then swing downwardly by gravity, opening switch 79, de-energizing solenoid 59, and opening valve 55. This will start turbine 36 and auxiliary pump 32, which will supply the necessary water to the tubes 18. The bell 83 will ring and give warning immediately to the without difficulty in almost any pumping system which utilizes main and auxiliary pumps. It has pro cn to be thoroughly reliable in operation, and will unfailingly serve to start the auxiliary pump when necessary to maintain the desired rate of flow. I

Having thus described my invention, what I claim as new and-desire to secure by Letters Patent is:

1. A control apparatus for an auxiliary pump arranged to discharge into a common system with a main pump .comprising a device to control the power supply to the auxiliary pump, a mechanism actuated automatically in accordance with variations in a force related to flow conditions in the discharge of the main pump which is effective to cause said device to start the auxiliary pump but which is ineffective to stop the same, and manually operable means to cause said device to stop the auxiliary pump after restoration of the desired flow conditions by the main pump.

2. A control apparatus for an auxiliary pump arranged to discharge into a common system with,

in a direction to start the auxiliary pump if the rate of flow drops to a predetermined minimum value but thereafter is ineffective to move the device in the opposite direction, and manually operable means to move said device back to its original position and stop the auxiliary pump afts er restoration of the desired rate of flow by the main pump.

3. A control apparatus for a fluid operated motor connected to drive an auxiliary pump arranged to discharge into a common system with a main pump comprising a valve to control the fluid supply to the motor, a pressure responsive mechanism actuated in accordance with pressure variations in the liquid discharged by the main pump, connections between said mechanism and the valve whereby the mechanism is effective to open the .valve under a predetermined pressure condition in said liquid discharged by the main pump but is ineffective to close the valve, and manually operable means to close the valve and stop the auxiliary pump after restoration of the desired pressure conditions by the main pump.

4. A control apparatus for an auxiliary pump arranged to discharge into a common system with a main pump comprising a movable device to control the power supply to the auxiliary pump, a solenoid to move the device, and a switch automatically actuated by a force related to the operation of the main pump and arranged to control the energization of the solenoid so as to move the device in a direction to start the auxiliary pump whenever the main pump fails to function in a desired manner but to control said solenoid so as to prevent the device from stopping the auxiliary pump after starting thereof.

5. A control apparatus for a fluid operated motor connected to an auxiliary pump arranged to discharge liquid into a common system with a main'pump comprising a valveto control the fluid supply to the motor, said valve being'biased toward its open position, a solenoid so arranged that when energized it will hold the valve closed against its bias, and a switch-arrangedto control the energization of the solenoid and to be automatically actuated by a force related to the flow. of the liquid so as to de-energize-the solenoid and open the valve whenever the main pumpfails to maintain predetermined liquid flow conditions, said switch being also constructed and arranged so that thereafter said force related to the flow of the liquid is inefiective to cause said switch to energize said solenoid to close said valve against its bias until it is rese by hand.

6. A control apparatus for a fluid operated motor conected to drive an auxiliary pump arranged to discharge into a common system with a main pump comprising a valve to control the fluid supply to the motor, said valve being biased toward open position, a solenoid so arranged that, when energized itwill hold'the valve closed against its bias, an electric switch biased toward open position and connected in a circuit with the solenoid and a source of electric current, a flexible diaphragm responsive to changes in a pressure differential which is a function of the rate at which liquid is discharged by the main pump, and means connecting the diaphragm with the switch which is so arranged that the switch will be held closed against its bias only so long as the pressure differential exceeds a predetermined minimum value.

7. A control apparatus for a fluid operated motor connected to drive an auxiliary pump arranged to discharge into acommon system with a main pump comprising a valve to control the fluid supply to the motor, said valve being biased toward open position, a solenoid so arranged that when energized it will hold the valve closed against its bias, a flexible diaphragm responsive to changes in an eflfective pressure which is a function of the rate of liquid flow in the discharge of the main pump, a horizontally slidable rod connected to move with the diaphragm, a member one end of whch is pivotally supported by a stationary pin and the other end of which has a projection normally resting on the rod, a mercury switch mounted onthe member and arranged to remain closed under normal conditions but to open whenever the rod releases the member and permits it to drop by gravity as a resultof a decrease in the liquid flow, and connections be- -tween the switch and the solenoid whereby the solenoid is energized only while the switch is closed. v I

8. A control apparatus as recited in claim 7 in which a second mercury switch is mounted on the member, and a bell is connected in an electric circuit with the second switch, said second switch being normally open and arranged to close when the member drops.

9. A control apparatus as recited in claim 'I in which means isprovided for adjusting the position of the supporting pin and thus varying the relative positions of the member and the slidable rod.

10. A steam generating apparatus comprising steam generating elements, a main pump arranged to deliver water thereto, an I auxiliary pump connected in parallel with the main pump, a movable device to control the power supply to the auxiliary pump, a mechanism actuated automatically in accordance with variations in a force related to the 'flow conditions in the discharge of the main pump and efiective to move said device only in adirection to start the auxiliary pump,

and manuallyoperable means to move said device whereby the steam and any unevaporated water are conducted from the tube, a pressure responsive device, means actuated by the pressure responsive device to control the operation of said water circulating, mechanism, and connections from the pressure responsive device to two points in the system close to the orifice and on opposite sides thereof so thatsaid device is controlled by the drop in pressure only through the orifice.

12. A control apparatus-for an auxiliarypump arranged to discharge a fluid into a common system with a main-pump comprising a device to control the power supply to the auxiliary pump, and a mechanism actuated by a force varying with variations in a condition related to the fluid flow in the system and effective to cause said device to start the auxiliary pump but ineffective thereafter to cause said device to stop the same.

13. A steam generating apparatus comprising a steam generating element, means to supplywater under pressure to one end of said element, means at said end of the element for restricting the flow of water as it enters said element thereby creating a drop in the pressure of the water flowing through the restricting means, and a mechanism immediately responsive to variations in said pressure drop and arranged to control the operation of the water supply means so as to maintain the flow of water into the element above a predetermined amount.

14. Steam generating apparatus comprising a steam generating element of the type in which the generated steam and the water from which it is being generated flow therein, means pro viding delivery of the water into said element, means providing a force varying with the rate of flow of water into said element, said means being arranged with respect to said element so that said force is opposed by and varies with the reaction of the force necessary to produce flow of the steam through the element, a regulating device responsive to variations in said force varying with the rate of flow of water into said steam generating element, and means actuated by the regulating device for controlling said delivery of the water into the steam generating element to provide suificient water for the steam generation therein.

15. Method of controlling the flow of water delivered to one end of a tube for generation of steam therefrom while flowing through said tube toward the other end thereof together with the steam, which comprises controlling the delivery of the water to the tube in accordance with variations in a force varying with the rate of flow of the water into the tube and opposed by and varying with variations in the reaction of the force of the generated steam flowing through said tube.

16. In a steam generating system of the type in which the steam is generated from water flowing in a closed water circuit in excess of the steam generated therefrom the method of insuring said flow of the water which comprises positively causing a flow of water in said circuit, producing sufliclent pressure in the water to cause delivery thereof into the portion of the circuit in which the steam is generated against the pressure of the steam generated and against the back pressure due to the steam flowing in said portion of the circuit, and controlling said flow of water in accordance with variations in a diflerence in pressure between said water pressure and the pressure of said generated steam within said steam generating portion of the circuit which is a measure of the rate of flow of the water into the steam generating portion of v the circuit and of the rate of steam generation therein.

17. A steam generating apparatus comprising a steam generating element, means to force water into said element, a conduit through which the steam and any excess water are removed from the element to maintain flow of steam through said element, a pressure responsive device, connections from said device to two points in the circulation system which are so located as to cause to act on said pressure responsive device a pressure difierential dependent in value upon the rate of flow of water into the element and upon a force opposing said pressure differential and varying with the rate 'of evaporation in and caused by flow of steam through the generating element, and means actuated by the pressure ;.'esponsive device for controlling the rate of flow of the water delivered into the element by said forcing means.

18. A control apparatus for an auxiliary pump arranged to discharge a fluid into a common system with a main pump comprising a device to control the power supply to the auxiliary pump, and a mechanism actuated in accordance with a variation in a force varying with a rate of flow of the fluid caused by the main pump, said mechanism being constructed and arranged so to control said device as to start said auxiliary pump when said rate of flow of fluid falls below a predetermined amount but being inefiective to cause said device to stop said auxiliary pump upon restoration of said flow.

WILLIAM S. ANDERSON, JR. 

